96x71 or 96x78 motor - That's the question Options

[KenH]

In playing with my el-cheapo dyno program it looks like you can get the same HP with either a 71mm or 78mm stroke. The 78mm however gives a bit more torque.

Over all the CAM seems to give the biggest improvement.

The question is - is it worth the hassle to go to 78mm stroke (T1 rods, special pistons, clearence issues, cost of rods, crank, pistons) for 10'lb of torque??

Looks like 96mm x 71mm with good heads, proper CAM, optimun fuel delivery, FI or Carb, will make a pretty good motor.

Comments??

Ken

[anthony]

Raby has graphs posted for all his engines at www. aircooledtechnology.com. You can use them a base of comparison against each other. The difference between his 2056 Daily Driver + and his 2270 Peformer is pretty substantial. Hope the chart works:

Torque
rpm......2056.......2270
2000......104.........129......+25
4500......130.........162......+32
5500......119.........144......+25
6000......104.........135......+31
6500.......?............122......+


HP
rpm......2056.......2270
2000.......40..........61........+21
4500......112........139.......+27
5500......125........151......+26
6000......104........154......+50
6500.......?...........151......+


To me the 2270 is clearly in a different league than the 2056. I did take a ride in McMarks 2056 equiped car with a mild cam. He dynoed it at 90hp at the wheels which would be about 105hp at the crank. I can say that it made the car move nicely - much much faster than my stock 160k mile 2L engine. To me his engine made the 914 feel like the car it always should have been. Still, I can't stop thinking that a 2270 would make the 914 faster than my 911SC and be comparable to most six conversions.

(IMG:http://www.aircooledtechnology.com/type4/914/2056_daily_plus.jpg)


(IMG:http://www.aircooledtechnology.com/type4/914/2270_performer.jpg)